Winter weather can be bitterly cold, and homeowners depend on a reliable furnace to keep the indoor environment warm and comfortable. While the build quality of a heating appliance is important, the installation process will have a greater impact on efficiency, comfort and unit longevity.

AFUE Ratings

ASHAE developed the Annual Fuel Utilization Efficiency (AFUE) standard to give consumers an easy way to compare the relative efficiency of different models and brands of furnaces. An AFUE rating is a reflection of the percentage of fuel the appliance consumes that is converted directly into heat energy. In a 90 AFUE rated furnace, only two percent of the burned fuel is exhausted as a waste gas. Recent Department of Energy standards mandate that furnaces installed in northern climates must have a minimum 90 AFUE rating while southern climate standards remain at 80 AFUE.

Older furnaces with standing pilot systems are usually less than 60 percent efficient. Aging units often require frequent costly repairs and contribute to greenhouse gas emissions. Upgrading to a new 98 AFUE rated furnace can save up to 39 percent in monthly operating costs when compared to a 60 AFUE rated model.

Proper System Design

If you are replacing an older furnace, it is critical to ensure your installing contractor runs a full set of ACCA Manual J load calculations before selecting the capacity of the unit. Unfortunately, many HVAC systems were installed without the benefit of legitimate sizing methods. Square feet per ton and other discredited formulas fail to account for a variety of factors that determine the unique energy consumption characteristics of every building.

In contrast, Manual J incorporates a number of important energy consumption metrics including:

* Building size
* Building orientation
* Glass style and exposure
* Insulation values
* Duck leakage
* Perimeter tightness
* Internal loads

A furnace that is installed without the benefit of comprehensive load calculations may short cycle, which can raise operating costs and reduce the usable life of the equipment. An improperly sized furnace can cause drafts, temperature fluctuations and humidity issues. Since larger systems are more expensive, homeowners pay for capacity they will never actually use.

Choosing the Equipment

Once the load calculations are completed, the installing HVAC contractor will provide equipment options based on capacity. High end furnaces incorporate better components, which will result in quieter operation, improved efficiency and even levels of comfort throughout your home. Homeowners can choose from a variety of options including two-stage burners and variable-speed blowers. These upgrades work in tandem to trim the burner flame and fan motor speed to precisely match the varying outdoor temperature conditions. Instead of simple on/off operation, the furnace adjusts to the meet the prevailing indoor load so that comfort and energy savings are maximized.

The Installation Process

Every new furnace installation begins with an analysis of the air distribution system. In retrofit applications, this includes a visual inspection of the ductwork to determine if there are any breeches, gaps or loose connections that need to be repaired. The duct system will also undergo a sizing test to ensure it conforms to the standards outlined in ACCA Manual D. Substandard ductwork can have a negative impact on air delivery and will degrade the performance of your new furnace if left uncorrected.

Once the ductwork is functioning properly, certified technicians begin the process of installing your new equipment. This includes removing the old furnace and setting the new equipment in place. Furnaces that are located in an attic require a second drain pan positioned under the unit for condensate protection.

When the equipment is set, the technician will begin the connection process by completing the following steps:

* Properly align the furnace
* Connect the furnace to the supply plenum and return ductwork
* Properly seal the connections
* Connect the gas line and check for any leaks
* Connect the condensate line
* Connect the flue pipe system to the furnace
* Connect the low-voltage thermostat wiring to the unit
* Make the final high-voltage electrical connections

Furnace Testing

Once the installation process is finished, the technician will start the unit and run it through a complete heating cycle. The temperature differential between the supply and return should meet or exceed the manufacturer’s specifications. Finally, the contractor will air balance the registers to ensure that every room in your home receives the exact amount of conditioned air required to maintain a comfortable, even temperature.